Product of glucoheptonic acid or its alkali metal salts and alkali metal hexametaphosphate



United States Patent 3,412,180 PRODUCT OF GLUCOHEPTONIC ACID OR ITSALKALI METAL SALTS AND ALKALI METAL HEXAMETAPHOSPHATE Hoyt M. Corley,Midlothian, Ill., assignor to W. H. Miner,

Inc., Chicago, Ill., a corporation of Delaware No Drawing. Filed Nov. 6,1964, Ser. No. 409,555 4 Claims. (Cl. 260-920) ABSTRACT OF THEDISCLOSURE Combining glucoheptonic acid or a salt thereof, such assodium glucoheptonate or potassium glucoheptonate, with an alkali metalphosphate, such as sodium hexametaphosphate, provides a new and highlyuseful sequestrant.

This invention relates to new and useful compositions of matter and theproduction thereof. More particularly it relates to unique compositionshaving unusually high sequestcring ability.

Compounds having sequestering ability, particularly for multivalentalkaline earth ions, have long been known. Those which are ofsignificant industrial importance are represented by theamino-carboxylic acids, such as the alkylene polymaine polyacetic acidsand the nitriloacetic acids; the sugar acids, such as the gluconic andglucoheptonic acids; and the alkali salts of various phosphates, such assodium tetrametaphosph-ate, sodium hexametaphosphate, sodiumtripolyphosphate, tetrasodium pyrophosphate, and the like.

Neither the organic nor the inorganic materials above referred to areentirely satisfactory, either because they have low specificsequestering ability, or are too expensive for many uses, or decomposeunder conditions necessary for use.

It is therefore an object of this invention to provide novelcompositions which are generally applicable for the sequestration ofobjectionable multivalent metal ions.

A further object is to provide a composition which has exceptionallyhigh specific sequestering ability, which is chemically stable underconditions of normal use, and which is low enough in cost to beeconomically attarctive.

Other objects and advantages of the invention will be-' come apparentfrom the description thereof which follows.

Sugar acids are believed to form water-soluble complexes withmultivalent metal ions because of the ability of the c-arboxyl andhydroxyl groups in those acids to bind the cations in ring form by meansof coordinate and covalent bonds.

They find their greatest field of utility in highly alkaline solutionswhere sequestration of iron is important. EX- actly how the iron issequestered by the sugar acids in alkaline solution is not fullyunderstood. Apparently carboxyl groups are not required, although acarbonyl group adjacent to the carboxyl appears to enhance sequesteringability. It may be that the hydroxyl groups on sugar acids formcomplexes with both ferric and ferrous ions. A most important industrialuse of the sugar acids is as a component of highly alkaline derustingand metal cleaning compounds and in bottle washing operations in highlyalkaline solutions, generally containing 3 caustic soda along with otherchemicals. On the other hand, the sugar acids are poor sequesteringagents for calcium, magnesium, iron, chrmoium, etc, in the pH range of4-10. The alkylene polyamine-polyacetic acids are the favored agents forsequestering these metals under mild condition of acidity or alkalinity.The latter mentioned sequestrants have less ability to hold iron withinthe pH range of 4-10 and almost no iron sequestering ability underconditions of high alkalinity such as is encountered in alkalinecleaning operations.

" "Ice I have discovered, however, that when the sugar acids andparticularly glucoheptonic acid and its sodium or potassium salts arecombined with an alkali metal phosphate such as sodiumhex-ametaphosphate, that for some unexplainable reason the combinationhas a tremendously increased sequestering ability over that which wouldb expected from the calculated values determined for the individualcompounds. The synergistic increase in the sequestering ability of thesetwo compounds When com- Ebined is illustrated in the following table,which compares the sequestering ability of the individual compoundsagainst combinations thereof in various proportions. In said table thesequestering ability of the individual compounds and combinations weretested for the amount of calcium carbonate sequestered using calciumphosphate as the indicator for determining the end point of sequesteringactivity.

TABLE I.SEQUESTERING ABILITY 0F SODIUM HEXA- METAPHOSPHATE ADDITIONS TOSODIUM GLUCO- HEP'IONATE Mg CaCO3/gm. of Sequestrant at pH 10Formulation Found Cale. Synergistic Afiect Dit.

1. Sodium glocoheptonate (357 sol)..-. 200.4 2. Sodium hexametaphosphate98% 421. 6 3. 99% #1, 1% #2 217.8 202.6 15.2 4. 98% #1, 2% #2.. 251. 4204. 8 46. 6 5. 967 #1, 4% #2-. 366.8 209. 2 157. 6 6. #1, 5% #2 467. 3211. 4 255. 9 7. 947 #1, 6% #2- 508. 9 213. 6 295. 3 8. 93% #1, 7% #2.593. 2 215. 8 388. 4 9. 90% #1, 10% #2 783. 5 222.5 56. 10

In the above examples it will be noted that the synergistic improvementis pronounced and where the sodium glucoheptonate solution is combinedwith at least 5% of the sodium hexametaphosphate, has a synergisticimprovement over 100%. My tests indicate that thes formulations alsohave a very high sequestering :power for copper, magnesium and iron aswell as calcium in the pH range of 611. There are 32 possible isomers ofglucoheptonic acid and in this patent wherever glucoheptonate isreferred to it is intended to cover the mixture of such isomers that arenormally present in the commercial production of glucoheptonic acid andits salts. Also by sodium hexametaphosphate I mean a sodium phosphatewhich has a ratio of Na O to P 0 in the range of 1.121/1 to 1.321/1.Preferably I use a material having a P 0 content of 66-67% and a pH of a1% solution of 7.8 to 8.0. I have found that even greater synergisticsequestering abilities are demonstrated when I combine the sodiumglucoheptonate solution with an alkali metal salt such as sodiumhexametaphosphate in the presence of heat.

Example 1 For example, 100 grams of sodium glucoheptonate solutionhaving a concentration of 50% solids was rapidly heated to 185 F. Assoon as the temperature reached 185 F., 50 grams of granular sodiumhexametaphosphate was added. At the end of 5 minutes the mass was cooleddown to F. as rapidly as possible and then to room temperature. Underthese conditions there seems to be a definite chemical reaction betweenthe sodium glucoheptonate and the sodium hexametaphosphate. There is anoticeable temperature increase to the boiling point of the liquid withsteam vapor being given off and the final reaction product is quitefluid. The total liquid volume changes very little during the reaction,not more than 24%. In the above example, the sodium glucoheptonatesolution which comprised the starting material was found in two separatetests to have a sequestering ability of 74.7 and 78 when measuredaccording to the buffered phosphate method of testing which will bedescribed below. The sodium hexametaphosphate by the same test methodshowed a sequestering ability of 400. The calculated sequesteringability of these proportions of sodium glucoheptonate andhexametaphosphate is 285 mg. of calcium carbonate per gram ofsequestrant. However the actual sequestering ability of this reactionproduct as determined by the phosphate testing method was 3703 in onetest and 3564 in the duplicate test.

Glucoheptonic acid and its salts are conventionally synthesized fromaldehyde sugars by the well-known Kiliani Synthesis, which consists inreacting a cyanide with an aldehyde group in an organic compound. Inaccordance with the present invention the aldehyde sugar may be obtainedfrom any one of the commonly available sugars, such as cane sugar, orsyrup made from any of the starches of Wheat, potatoes, soybeans, hardwoods and the like. The cyanide reaction with the aldehyde sugar isexothermic, causing a considerable temperature rise in the reactionmass. The end of the reaction can therefore be determined by the pointat which there is no further temperature rise. The aldehyde enolizes toform an unstable hydroxy group at the aldehydic oxygen. This unstablehydroxy group reacts with the cyanide to form a nitrile of the organiccompound and a hydroxide with the anion on the starting cyanidecompound. When this reaction is conducted with an organic compoundhaving multi-functional groups, the nitrile is easily hydrolyzed 'to acarboxyl group. One molecule of water reacts with the nitrile to givethe corresponding amide. Then a second molecule of water reacts with theamide to give a carboxyl group and releases ammonia. The carboxyl groupis stable and can be subjected to numerous additional reactions.

Example 2 In another example, sodium glucoheptono-hexameta phosphatereaction product of Example 1 was produced by charging 281 lbs. of waterinto a jacketed autoclave equipped with an agitator and a sparger in thebottom to accomplish aeration. The water was heated in the autoclave to60 F. and with the agitator in operation it was charged with 304 lbs. ofan aldehyde sugar obtained from cornstarch. The particular cornstarchused in the example is sold under the trade name Sweetose C and isdescribed by its manufacturer as follows:

Weight, lbs. per gal. at 100 F. 11.8 Percentage ash (sulphated) ofresin-refined corn syrup less than 0.02%. Percentage ash of bone-0.3%char or vegetablecarbon refined corn syrup 0.3%.

After charging the autoclave with the sweetose C a 4 which indicated thereaction to produce sodium glucoheptonate was complete.

As soon as the temperature rise stopped 260 lbs. of granular sodiumhexametaphosphate was added to the autoclave. The temperature roseapproximately 212 F. with the evolution of steam. Aeration was startedjust before the hexametaphosphate was added and was continued untilafter the reaction was completed. After a delay of 5 minutes the masswas cooled as rapidly'as possible until the temperature reached F., atwhich time the agitation and aeration were stopped.

Ideally, the concentrated sodium glucoheptono-hexametaphosphate reactionproduct is diluted with cold water at the end of the first 5 minutes ofreaction time in an amount sufficient to give a final sequesteringability of 250-500 mg. of calcium carbonate per gram of diluted solutiondepending upon the sequestering ability it is desired to have in thefinished product. By using large volumes of water to dilute theconcentrate, it is possible to greatly expedite the cooling of thereaction mass and also prevent decomposition of the unreactedpolysaccharides as well as the glucoheptono-hexametaphosphate reactionproduct.

One of the problems of this reaction is the heat instability of sugar,syrups and sodium glucoheptonate, which easily decompose at elevatedtemperatures. I have found, however, that limiting the time the reactionmass is held at F., coupled with rapid cooling of the reaction productminimizes degradation. For example, we have found that maintaining the185 F. temperature in the reaction mass for 15 minutes, after the sodiumhexametaphosphate has been added, reduces the sequestering ability ofthe reaction product by approximately 50%. It also greatly increases theviscosity of the solution and darkens it substantially. Solutions heldfor 15 minutes at 185 F. are black as compared with the brown colorationobtained during the five-minute time required for reaction.

Example 3 For comparison purposes, a commercial form of sodiumglucoheptonate, a light colored, 97%. pure, sodium glucoheptonate inpowder form, was tested for its sequestering ability and was then usedfor reacting with sodium hexametaphosphate according to the presentinvention. In this instance 4.1 grams of the above-mentioned 97% sodiumglucoheptonate was mixed with distilled water to produce 10 ml. ofsolution. This 41% solids mixture gave a sequestering ability of 84:6 inthe first test and 74.7 mg. of calcium carbonate per gram of solution inthe second test. 8 grams of this sodium glucoheptonate solution washeated to 185 F. Aeration was started and 4 grams of granularhexametaphosphate added to the solution. Heating and aeration wascontinued for 5 minutes, after which the reaction mass was rapidlycooled. The sequestering ability of the mixture of these two materialsshould :have been 256 by calculation. In the first test its sequesteringability was actually determined to be 2,119.8 and in the second test tobe 2,189.5 mg. of calcium carbonate per gram of test solution.

The method employed for determining the sequestering ability of theglucoheptonate and its esters of hexametaphosphate in the above exampleswas conducted as follows:

A sample of the sequestering agent to be tested was made up as a 0.3%solution in distilled water, and 10 m1. of saturated potasium dihydrogenphosphate (KH PO was added per 100 ml. of solution. The concentration ofKH PO in the test solution was 2.2 grams per 100 ml. The pH of thesolution to be tested was adjusted as necessary by the addition ofsodium hydroxide solution. Test solutions of calcium, magnesium and ironwere made such that their concentrations were 1 milligram of metallicion per ml. In the case of magnesium the solution 'was magnesiumsulfate, in the case of calcium the solution was calcium chloride, andin the case of iron the solution was ferric chloride. In making eachtitration, the solution of the test ion was added slowly to the solutionof the sequestering agent, and the end point considered to be that atwhich the first permanent turbidity appeared. The pH was moniteredduring the course of each titration and was adjusted as necessary inorder to maintain a constant pH.

It is assumed that sequestering agents work on a mole to mole basis,that is, one mole generally of a sequestrant can adsorb and hold onemole of heavy metal ion only. However, in the sodium glucoheptono-sodiumhexametaphosphate product which We obtain, some 410 moles of multivalentmetal ion per mole of glucoheptono-hexametaphosphate product are beingsequestered and this ability to sequester multiple ions per mole ofsequestrant is not yet explainable to my satisfaction; however, mytestings substantiate its existence. In the above example I have foundthat one gram mole of sodium glucoheptonosodium hexametaphosphateproduct will hold 4 gram moles of calcium ion in aqueous solutionwhereas on a 1 to 1 mole proportion basis it should require 848 grams ofthis complex to hold 40 grams of calcium ion (equivalent to 100 grams ofcalcium carbonate) in solution.

Thus having described my invention, I claim:

1. The sequestrant obtained by combining from about 50 to 99 parts of amaterial from the group consisting of iglucoheptonic acid and the sodiumand potassium salts thereof with from about 50 to about 1 parts of analkali metal phosphate having an Na O to P 0 ratio in the range of1.121/1 to 1.321/1.

2. The product obtained by combining from about 50 to 99 parts of sodiumglucoheptonate 'with from about 50 to 1 parts of a sodium phosphatehaving an Na O to P 0 ratio in the range of 1.121/1 to 1.321/1.

3. The sequestrant obtained by adding to an aqueous solution containingsodium glucoheptonate, which solution is at a temperature of about 185R, an amount of sodium hexametaphosphate equal to the amount of sodiumglucoheptonate and after about 5 minutes, cooling the reaction mixture.

4. The sequestrant obtained by heating an aqueous solution of alkalimetal glucoheptonate to about 185 F., combining granular alkali metalhexarnetaphosphate therewith at said temperature, and after about 5minutes, cooling the reaction mixture, the amount of said glucoheptonatebeing equal to the amount of said hexametaphosphate.

No references cited.

CHARLES E. PARKER, Primary Examiner.

A. H. SUTTO, Assistant Examiner.

